1. Field Of The Invention
This invention relates generally to systems for gravel packing a production zone of a well, and more particularly, to a system including a hydraulically activated device for setting a liner hanger of such a system.
2. Description Of The Prior Art
Unconsolidated formations, particularly those containing loose sands and sandstone strata, present constant problems in well production due to migration of loose sands and degraded sandstone into the well bore as the formation deteriorates under the pressure and flow of fluids therethrough. This migration of particles may eventually clog the flow passages in the production system of the well, and can seriously erode the equipment. In some instances, the clogging of the production system may lead to a complete cessation of flow, or killing of the well.
One method of controlling sand migration into a well bore consists of placing a pack of gravel on the exterior of a perforated or slotted liner or screen which is positioned across an unconsolidated formation to present a barrier to the migrating sand from that formation while still permitting fluid flow. The gravel is carried to the formation in the form of a slurry, the carrier fluid being removed and returned to the surface. The proper size of gravel must be employed to effectively halt sand migration through the pack, the apertures of the liner or screen being gauged so that the gravel will settle out on its exterior, with the slurry fluid carrying the gravel entering the liner or screen from its exterior and being circulated back to the surface.
Prior to effecting the gravel pack, drilling mud and other contaminants may be washed from the well bore, and the formation treated. Commonly employed treatments include acidizing to dissolve formation clays, and injecting stabilizing gels to prevent migration of formation components and formation breakdown prior to packing.
Subsequent to effecting the gravel pack, a reverse circulation technique may be utilized to remove remaining gravel laden slurry from the operating string utilized to conduct the slurry. With such a reverse circulation technique, the direction of circulation is reversed and a clean fluid is pumped down the path previously utilized for returning the slurry fluid, and the remaining gravel laden slurry will be forced back up the path originally used to conduct the gravel laden slurry down to the well.
A typical prior art gravel packing system is shown in U.S. Pat. No. 4,180,132 to Young, and assigned to Otis Engineering Corporation. This patent discloses a setting device for a gravel packing system which includes a hydraulically actuated piston 192 for setting the compressible packing element of the packer located therebelow as seen in FIGS. 10A-10E thereof. This device also includes a liner valve located below the packet as seen in FIG. 10E. The setting device includes a valve sleeve 230 having a closed lower end. The valve sleeve 230 can be pumped open to direct gravel laden slurry to the liner valve ports 100 as seen in FIGS. 11E and 11F. The setting device also includes a sliding sleeve type return valve at its upper end, which is arranged to be closed when weight is set down on the setting device.
Another prior art gravel packing system including a hydraulically actuated piston for setting the packer is shown in U.S. Pat. No. 3,987,854 to Callihan et al., and assigned to Baker Oil Tools, Inc. The details of construction of the setting device and packer of the Callihan et al. patent are best seen in FIGS. 4A-4E and 5A-5E thereof.
U.S. Pat. No. 3,678,998 to Cockrell et al., and assigned to Baker Oil Tools, Inc., discloses a retrievable wireline set well packer, which is similar in a number of aspects to the packer disclosed in the Callihan et al. U.S. Pat. No. 3,987,854 patent, and which is constructed to be retrieved by means of a retrieving tool.
Another typical prior art gravel packing system is shown in U.S. Pat. No. 4,049,055 to Brown, and assigned to Brown Oil Tools, Inc. This system includes a hydraulic piston for setting a retrievable compression packer of the gravel packing system. The packer can subsequently be released and retrieved by the use of a retrieving tool seen in FIG. 3.